Greetings, for a variety of reasons I program my own workouts most of the time. I really enjoy doing hill sprints but don't know exactly what they accomplish, or how often they should be done. My ideal session is on a hill about 50 yards, steep enough that sprinting to the top is difficult, but not so steep that I'm not moving at the top. Usually 10 reps, with a walk down as recovery.

They help improve speed, leg drive, and mental toughness. You can vary up the training adaptation you get by adjusting rest periods, whether you go at 100% effort and expect to get slower from one to the next or go at 90% effort and maintain a consistent pace, etc. Not sure what else you're looking for.

If you're trying to get faster I'd also recommend throwing in some sprints on a slight downhill and some footspeed agility work so your legs also get accustomed to turning over faster. Running uphill will improve your ability to drive harder with each step but a quick foot turnover is also important to speed. That being said, I've never been a fast sprinter so for speed advice look at some stuff about how sprinters train...I mainly use hills for conditioning rather than pure speed.

Hill sprinting is the single exercises that trashes me the most, by far. I mean, I have felt trashed after workouts before, after a metcon or a set of 20-rep ATG squats with what is heavy (for me, about 200#)... but these are longer efforts.

There is a very steep hill that I've done a few workouts on, I timed myself and it takes me about 21 seconds to get to the top. At the top it almost feels like I can't move my legs, it's very steep, definitely much more than the 15 degrees mentioned in the link provided above. The thing is, it takes me FOREVER to recover from this single 21 seconds effort. I don't know why. It takes several minutes, it takes longer than a set of 20-rep squats (which probably takes 90 secs or more?? never timed that). It also seems to take longer or as long as some metcons, but these have been MUCH longer than 21 mere seconds. I just can't comprehend how I feel so trashed, so out-of-breath after such a short period of time. So I usually rest a full 10 minutes (which do NOT feel like enough time!!!!) and just do 3 of these runs. That's it. I can't imagine doing anything else. It just kills me. So I have a love-hate relationship with hill sprints. I should point out I go all-out on these. If I were to jog it, as I once did, I did 10 trips up+down in about 14 minutes. But I find the 3 max effort trips with 10 minutes rest actually to be harder!!! If one is to judge effectiveness by how difficult things are.... then hill sprints must be VERY effective, lol.